Well all that is covered in Florida Statutes ch 765, a proxy or guardian has the authority but there must also be other conditions.
Greer didn't require and exam of Terri before they stopped feeding her. That's another violation, one of many.
In addition, the woman can swallow, she has been tube fed due to her husbands threats to not feed her any other way. They removed the tube, but if she isn't able to swallow, why the arrest of people trying to bring her water? why not let a priest in to allow communion? why deny her fluid?
My point is she is not being kept alive by feeding tube, if she can swallow. It's not removal of life support, it's is death by starvation. Quite different.